BlamePointTracer is not providing any data

I changed our configuration to use BlamePointTracer (as recommended). Doing that I just changed the tracer (and adapted the metric name). Before the change I got information from the associated classes, after the change I get nothing at all. As I just changed the tracer and our application did not change, problems regarding incorrect class namings etc. cannot be the reason.

Here is a snippet of how I use the BlamePointTracer. Could you see any problem with this definition?